Filtration apparatus

ABSTRACT

A cleansing tank  38  and a screw conveyor  32  are removably mounted to a mounting opening  22  of a filtration tank  2 . When the cleansing tank  38  and the screw conveyor  32  are to be removed, they can be extracted to the exterior of the filtration tank  2 , by detaching a base  28 , which axially supports the screw conveyor  32 , from a rim  24 . Purified water is backwashed through a purified water discharge pipe  60  when the cleansing tank  38  and the screw conveyor  32  are extracted and inserted through the mounting opening  22 . This causes filtration media  14  to float, thereby reducing the resistance thereof.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a filtration apparatus for filteringliquids such as water. Particularly, the present invention relates to afiltration apparatus, to the interior of which a filtration mediacleansing mechanism is mountable.

BACKGROUND ART

Conventionally, at large scale water treatment facilities such as waterpurification plants, water purification processes are performed by:removing fine suspended matter by filtering water through a layer offiltration media such as filtration sand; then by disinfecting thefiltered water with chlorine. As cleansing methods of the filtrationmedia, surface cleansing, which washes the surface of a sand layer byhitting it with water sprayed from a nozzle, and backwash cleansing,which forces purified water into a filtration reservoir from a lowerpressure compartment, thereby floating the filtration sand grains,causing them to rub against each other, are in common use. However, ifthe backwash cleansing is repeated over a long period of time, the waterpressure thereof influences even a gravel layer, creating areas ofdifferent thickness in said layer, which is optimally flat and of aneven thickness. In addition, the surface cleansing and backwashcleansing methods cannot cleanse the filtration media with satisfactoryefficacy. Problems arise from repeated use over a period of time such ascontaminant accumulation on the filtration media. In this case, it isnecessary to perform a regeneration process, which involves: totallyceasing the operation of the filtration reservoir, removing thefiltration media, cleansing the filtration media, and replacing thecontaminated filtration media, which has been cleansed. However, theregeneration process is extremely costly, and as during said process thefiltration reservoir is not operating, it leads to a decrease in watertreatment efficiency.

The applicant of the present invention, in order to meet this demand,has developed and proposed a sand cleansing apparatus which cleansespolluted filtration media in a shorter time and with a higher degree ofcleansing ability (Japanese Unexamined Patent Publication Nos.10(1998)-109051 and 11 (1999)-057526). This sand cleansing apparatuscomprises: a sand receiving opening for receiving filtration media drawnfrom a filtration reservoir in its upper portion; a cleansing tank whichstores sand and cleansing water having a sand extraction opening; aagitation tank erected within said cleansing tank having openings on theupper and lower ends thereof; and a screw conveyor which rotates withinsaid agitation tank. The grains of sand are brought upward by the screwconveyor along with the cleansing water. As they are being conveyedupward, said grains of sand rub against each other by being agitated,and the scrubbing action thereof effectively removes the contaminantsthat are attached or coated thereon.

Filtration apparatuses, such as filtration tanks, which are installed insmall scale simple plumbing networks or factories, differ from the largescale water purification plant described above. It is not practical toemploy the sand cleansing apparatuses proposed by the present applicants(Japanese Unexamined Patent Publication Nos. 10(1998)-109051 and11(1999)-057526) in these filtration apparatuses. This is because theutilization scales of the filtration apparatuses are small. Therefore,it is not efficient to secure space to install the sand cleansingapparatus in, and to expend costs associated with the installation andremoval of the sand cleansing apparatus, when compared to the case ofthe filtration reservoir.

There are known filtration devices, as disclosed in Japanese Patent No.31491 and Japanese Unexamined Utility Model Publication No.63(1988)-98704, which have been developed in view of these points. Thefiltration device disclosed in Japanese Patent No. 31491 comprises acentral pipe (cleansing tank), which is suspended by a frame (supportportion). The lower end of the central pipe opens within a filtrationchamber (filtration tank). A propeller is provided within the interiorof the central pipe, at its lower end. A pipe having a jet expulsionopening is provided above the propeller, the jet expulsion opening beingslightly above the upper edge of the central pipe. The pipe having thejet expulsion opening is linked to the propeller, and rotates therewith,to spray cleansing fluid in the horizontal direction by use ofcentrifugal force. During filtration, water having contaminants issupplied from above, and is filtered by passing through filtration sand,which is provided on an apertured false bottom (filtration floor).During cleansing, the propeller is rotated, causing filtration sand tobe suctioned into the central pipe via the lower opening thereof. Thefiltration sand is elevated through the central pipe, then discharged inthe horizontal direction by the cleansing fluid being sprayed from thejet expulsion opening. The filtration sand is cleansed by contaminantsbeing separated therefrom at this time.

The filtration device disclosed in Japanese Unexamined Utility ModelPublication No. 63-98704 comprises an elevating pipe (cleansing tank)erected therein, and a spiral water elevator provided within theelevating pipe. During filtration, water is discharged by a waterdispersing tube, which is within filtration sand. Processed water, whichhas been filtered by passing through the filtration sand from below, isdischarged above the filtration sand. During cleansing of the filtrationsand, the spiral water elevator rotates and elevates the filtrationsand, which has trapped contaminants, from the lower portion of thespiral water elevator. The contaminants are separated from thefiltration sand by use of centrifugal force. The filtration sand isexpelled through a filtration sand expulsion opening, which is providedin the upper portion of the elevating pipe.

Wear of the aforementioned propeller, central pipe, spiral waterelevator and the elevating pipe is unavoidable over long term use, dueto the relative movement among them and the filtration sand.Accordingly, the frequency of part replacement in the aforementioneddevices is high.

In the filtration device disclosed in Japanese Patent No. 31491, theframe, to which the central pipe (cleansing tank) for cleansing thefiltration media and the propeller is mounted, is suspended from aconduit pipe, which is provided at the upper portion of the filtrationtank. However, the central pipe has a diameter far greater than theframe, and it cannot be dismounted from the conduit pipe to the exteriorof the filtration tank. Accordingly, when the propeller or the centralpipe become worn by the filtration media, it becomes necessary todisassemble the filtration tank to remove the propeller and thecleansing tank. In addition, filtration cannot be sustained, becauseagitation of the filtration media by the propeller crushes thefiltration media (the properties of the filtration sand are changed).

In the filtration device disclosed in Japanese Unexamined Utility ModelPublication No. 63-98704, the spiral water elevator is provided in anelevating pipe, which is formed integrally with a expulsion spout,through which filtered water is expelled. However, the elevating pipe isnot configured to be removable from within a tank (filtration tank) Inaddition, the spiral water elevator is axially supported by smallopenings above and below it, and is also of a configuration that doesnot enable removal from within the tank. For these reasons, it isextremely difficult to exchange the elevating pipe and the spiral waterelevator.

SUMMARY OF THE INVENTION

The present invention has been developed in view of the points describedabove. It is an object of the present invention to provide a filtrationapparatus, in which a cleansing tank and a screw conveyor are easilyreplaced, thereby facilitating maintenance thereof.

It is a further object of the present invention to provide a low costfiltration apparatus, in view of the fact that filtration apparatuseshaving cleansing mechanisms built in are expensive.

The filtration apparatus of the present invention is a filtrationapparatus for filtering liquid, which is introduced into a filtrationtank, and discharging filtered liquid to the exterior of the filtrationtank, comprising:

-   -   the filtration tank that houses filtration media; and    -   a filtration media cleansing mechanism that comprises a hollow        cleansing tank for cleansing the filtration media; and a        contaminant expulsion means for expelling contaminants separated        from the filtration media to the exterior to the filtration        tank; wherein:    -   the cleansing tank is a cylindrical body that hangs within the        filtration tank from the upper portion thereof;    -   the cleansing tank is provided with a lower opening at a        position lower than the upper surface of the filtration media        housed in the filtration tank, and a plurality of upper openings        at a position higher than the upper surface of the filtration        media;    -   the cleansing tank is provided with a screw conveyor for        conveying the filtration media and the liquid, which enter the        cleansing tank from the filtration tank via the lower opening,        upward from the lower opening to the upper openings while        scrubbing the filtration media within the cleansing tank;    -   a mounting opening, to which the upper portion of the cleansing        tank is removably attachable, is provided at the upper portion        of the filtration tank; and    -   a cleansing portion, comprising the cleansing tank, the screw        conveyor, and a drive mechanism for the screw conveyor, is        removably attachable to the filtration tank via the mounting        opening, from the exterior of the filtration tank.

It is preferable that the cleansing portion is configured so that thelower end of the screw conveyor protrudes downward from the loweropening of the cleansing tank.

A configuration may be adopted, wherein:

-   -   the cleansing portion is constructed by a plurality of arts,        which are detachably linked so as to separate in the axial        direction of the screw conveyor.

A configuration may also be adopted, wherein:

-   -   slots that enable the filtration media to pass therethrough are        formed at the lower portion of the cleansing tank so that at        least a portion of the slots are below the upper surface of the        filtration media.

A configuration may further be adopted, wherein:

-   -   a plurality of gaps that extend along the outer periphery of the        axis of the screw conveyor are formed in the interior sides of        the blades of the screw conveyor.

The filtration tank may be filled with the liquid to be filtered so thatthe liquid surface is at least at the upper openings of the cleansingtank.

The filtration apparatus of the present invention is also a filtrationapparatus for filtering liquid, which is introduced into a filtrationtank that houses filtration media, and discharges filtered liquid to theexterior of the filtration tank, wherein:

-   -   a mounting opening that the filtration media is visible through        is provided in the filtration tank above the filtration media;    -   a removably attachable lid is provided to cover the mounting        opening; and    -   the lid is removed during cleansing of the filtration media, to        insert and fix a cleansing means in the mounting opening, the        cleansing means comprising a hollow cleansing tank, a screw        conveyor for conveying the filtration media and the liquid        upward while scrubbing the filtration media within the cleansing        tank, and a drive mechanism for the screw conveyor, to perform        cleansing of the filtration media.

The filtration apparatus of the present invention comprises thefiltration tank, the hollow cleansing tank for cleansing the filtrationmedia within the filtration tank, and the filtration media cleansingmechanism. The cleansing tank is a cylindrical body, which is suspendedwithin the filtration tank from above. The screw conveyor, for conveyingthe filtration media and the liquid upward from the lower opening to theupper openings of the cleansing tank while scrubbing the filtrationmedia, is provided within the cleansing tank. The mounting opening, forremovably mounting the upper portion of the cleansing tank, is providedat the upper portion of the filtration tank. The cleansing portion,comprising the cleansing tank, the screw conveyor, and the drivemechanism for the screw conveyor, is removably mounted to the mountingopening. Therefore, the following advantageous effects are exhibited.

In the case that the cleansing tank and the screw conveyor are worn byrelative movement with the filtration media, they can be removed fromthe upper portion of the filtration tank. The worn parts may be replacedby inserting them through the upper portion of the filtration tank.Accordingly, maintenance of the filtration apparatus is facilitated.

A configuration may be adopted wherein the lower end of the screwconveyor protrudes from the lower opening of the cleansing tank. In thiscase, the filtration media is easily pushed upward into the cleansingtank by the lower end of the screw conveyor during cleansing. Therefore,the cleansing efficiency is improved.

A configuration may be adopted wherein the cleansing portion isconstructed by a plurality of parts, which are detachably linked so asto separate in the axial direction of the screw conveyor. In this case,even if the filtration apparatus is installed indoors in a room with alow ceiling, removal of the screw conveyor is facilitated by separatingthe cleansing portion. Accordingly, maintenance of the cleansing portionand the interior of the filtration apparatus, and replacement of thescrew conveyor and the like, can be performed without being restrictedby the installment location of the filtration apparatus.

A configuration may be adopted wherein slots that enable the filtrationmedia to pass therethrough are formed at the lower portion of thecleansing tank so that at least a portion of the slots are below theupper surface of the filtration media. In this case, the filtrationmedia easily flow into the cleansing tank through the slots. Therefore,the filtration media is easily housed within the cleansing tank as well,increasing the filtration function within the cleansing tank.

A configuration may be adopted wherein a plurality of gaps that extendalong the outer periphery of the axis of the screw conveyor are formedin the interior sides of the blades of the screw conveyor. In this case,the following advantageous effects are exhibited. It is possible toreduce resistance of the filtration media, by performing backwashcleansing during removal of the cleansing tank and the screw conveyor,thereby causing the filtration media to float. At this time, liquidenters the cleansing tank through the gaps to enter the cleansing tank,more effectively causing the filtration media to float. Therefore,removal of the cleansing tank and the screw conveyor is furtherfacilitated. In addition, back wash cleansing may be performed prior todriving a motor for the screw conveyor during cleansing. At this timealso, the motor can be driven with low resistance by causing thefiltration media to float in a similar manner.

The filtration tank may be filled with the liquid to be filtered so thatthe liquid surface is at least at the upper openings of the cleansingtank. In this case, the liquid enters the cleansing tank easily,enabling active filtration to be performed within the cleansing tank.

In addition, the filtration apparatus is of a configuration wherein themounting opening that the filtration media is visible through isprovided in the filtration tank above the filtration media, and aremovably attachable lid is provided to cover the mounting opening. Thelid is removed only during cleansing of the filtration media, to insertand fix the cleansing means in the mounting opening, the cleansing meanscomprising the hollow cleansing tank, the screw conveyor for conveyingthe filtration media and the liquid upward while scrubbing thefiltration media within the cleansing tank, and the drive mechanism forthe screw conveyor, to perform cleansing of the filtration media.Therefore, the following advantageous effect is exhibited.

That is, the cleansing means is not necessary during normal filtration.Therefore, the filtration apparatus may be provided at low cost,reducing an initial investment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the main parts of a filtration apparatusaccording to a first embodiment of the present invention.

FIG. 2 is a front view of a screw conveyor, which is utilized in thefiltration apparatus of FIG. 1.

FIG. 3 is a sectional view of the screw conveyor, taken along the line3-3 in FIG. 2.

FIG. 4 is a sectional view of the main parts of a filtration apparatusaccording to a second embodiment of the present invention.

FIG. 5 is a sectional view of the main parts of a filtration apparatusaccording to a third embodiment of the present invention.

FIG. 6 is a partial magnified view of the vicinity of a mounting openingof the filtration apparatus of FIG. 5.

FIG. 7 is a sectional view of the main parts of the filtration apparatusof FIG. 5, illustrating the process of removing a motor from thefiltration apparatus.

FIG. 8 is a sectional view of the main parts of the filtration apparatusof FIG. 5, illustrating the process of removing a base from thefiltration apparatus.

FIG. 9 is a sectional view of the main parts of the filtration apparatusof FIG. 5, illustrating the process of removing a lower shaft from thefiltration apparatus.

FIG. 10 is a sectional view of the main parts of the filtrationapparatus of FIG. 5, illustrating the process of removing a cleansingtank from the filtration apparatus.

FIG. 11 is a sectional view of the main parts of a filtration apparatusaccording to a modification of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the filtration apparatus of the present invention will bedescribed in detail with reference to the attached drawings. FIG. 1 is asectional view of the main parts of a filtration apparatus according toa first embodiment of the present invention. FIG. 2 is a front view of ascrew conveyor, which is utilized in the filtration apparatus of FIG. 1.FIG. 3 is a sectional view of the screw conveyor, taken along the line3-3 in FIG. 2. FIG. 4 is a sectional view of the main parts of afiltration apparatus according to a second embodiment of the presentinvention.

As illustrated in FIG. 1, the filtration apparatus 1 according to thefirst embodiment of the present invention comprises: a substantiallycylindrical filtration tank 2 having closed upper and lower ends; afiltration floor 4, which has a great number of fine apertures (notshown) and is provided horizontally at a lower portion of the interiorof the filtration tank 2; and a filtration media cleansing mechanism 6,which is mounted to a curved upper wall 20 of the filtration tank 2. Aplurality of supporting legs 8 (only one is shown in the figure) aremounted on the filtration tank 2. The filtration tank 2 is installed ona floor 10 via the supporting legs 8. A great number of shortcylindrical ceramic filters 12, which have fine apertures, are providedon the filtration floor 4. The filters 12 have strength to withstandfiltration media 14 that accumulates on the filtration floor 4, andwater (liquid) 16 within the filtration tank 2. The filters 12 operateto efficiently pass only purified water 16 below the filtration floor 4.

Radially extending recesses 18 are formed in the central portion of thefiltration floor 4. Filters 12 are also provided within these recesses18, causing the height of the filters 12 at the central portion of thefiltration floor 4 to be low. The reason for forming the recesses 18will be described later.

A circular mounting opening 22 is formed at the central portion of theupper wall 20 of the filtration tank 2. The filtration media cleansingmechanism 6 is mounted in the mounting opening 22. The periphery of themounting opening 22 is formed into a rim 24 for mounting. A base 28, onwhich a motor 26 and a brake mechanism 27 are mounted, is mounted on therim 24. A holding portion 36, which has bearings 30 at three locations,is formed within the base 28. The bearings 30 at the three locationsrotatably support a shaft 34 of a screw conveyor 32.

Next, the filtration cleansing mechanism 6 will be described in detail,with reference to FIG. 2 and FIG. 3 as well. A cleansing tank 38, whichis a cylindrical body, is provided with a discoid partition wall 29 atthe upper portion thereof. A flange 31 at the outer periphery of thepartition wall 29 is mounted onto the rim 24, and secured thereto withbolts, along with the base 28. Accordingly, it is necessary that themounting opening 22 is of a size that enables the cleansing tank 38 topass therethrough. In this manner, the upper portion of the cleansingtank 38 is mounted onto the rim 24, and substantially the entirety ofthe cleansing tank 38 is suspended from the upper wall 20. An aperture33 that engages the holding portion 36 to form a seal therewith isformed in the center of the flange 31. Thereby, the interior of thefiltration tank 2 is maintained in a sealed state during filtration.

The lower portion of the cleansing tank 38 is open, to form a circularlower opening 40. A plurality of upper openings 42 that extend in thevertical direction are formed at predetermined intervals in the upperportion of the cleansing tank 38. The positional relationship betweenthe filtration media and the lower opening 40 is determined so that thelower opening 40 is positioned within the filtration media 14. The screwconveyor 32 is provided within the interior of the cleansing tank 38. Asillustrated in FIG. 1 and FIG. 2, the shaft 34 of the screw conveyor 32comprises a reduced diameter portion 34 a and a large diameter portion34 b. The reduced diameter portion 34 a is supported by the bearings 30.A link portion 46, for linking the shaft 34 with the motor 26, is formedat the upper end of the shaft 34. The large diameter portion 34 b, whichis provided to add strength to the shaft 34, is a hollow pipe with aclosed end 44. A spiral screw blades 43 is formed on the large diameterportion 34 b. The blade 43 is formed to the lower end 44 of the shaft34.

As shown in FIG. 3, a gap 48 is formed in the inner periphery of theblade 43, along the outer periphery of the shaft 34. In the presentembodiment, the gap 48 is formed continuously along the outer peripheryof the shaft 34. The blade 43 is linked to the shaft 34 by welding linkpieces 50 (supporting members) thereto at predetermined intervals. Notethat the gap 48 and the link pieces 50 are omitted from FIG. 1 and FIG.2. The gap 48 is formed continuously in the present embodiment. However,a plurality of gaps may be formed along the outer periphery of the shaft34. In this case, the link between the shaft 34 and the blade 43 maybeestablished by support members which are integrally formed with theblade 43, instead of the separate link pieces 50.

The aforementioned gap 48 (ribbon space) between the outer periphery ofthe shaft 34 and the blade 43 is set to be within a range from 1% to 98%of the area of the blade 43. Preferably, the gap is set to be within arange from 30% to 60%. If the gap 48 is not provided, the filtrationmedia 14 does not sufficiently enter the cleansing tank 38 duringbackwash cleansing, to be described later. However, if the gap 48 isexcessively large, the filtration media 14 becomes difficult to conveytoward the upper portion of the cleansing tank 38 during cleansing.Accordingly, the appropriate area ratio of the blade 43 and the gap 48is set as described above.

The link portion 46 at the upper end of the screw conveyor 32 is linkedto the brake mechanism 27 of the motor 26 via a coupling 52. When theblade 43 of the screw conveyor 32 is placed within the cleansing tank 38in this manner, the upper end of the blade 43 is positioned in thevicinity of the lower edges 42 a of the upper openings 42, asillustrated in FIG. 1. In addition, the lower portion 35 of the screwconveyor 32 (refer to FIG. 1) protrudes downward from the lower opening40 of the cleansing tank 38, and the lower end 44 of the shaft 34 ispositioned in the vicinity of the filtration floor 4. This configurationenables the most efficient cleansing of the filtration media 14 in thevicinity of the filtration floor 4 during cleansing of the filtrationmedia 14. The outer peripheral edge 54 of the screw conveyor 32 (referto FIG. 3) is placed so as to form a slight gap between it and the innerperipheral surface of the cleansing tank 38. The dimension of the gap isapproximately two to three times the particle diameter of the filtrationmedia 14. The gap may be larger, but the maximum allowable size of thegap is approximately 30 mm. The gap is provided to reduce thepossibility of the filtration media 14 being crushed, in the case thatthe filtration media 14 is trapped between the blade 43 and thecleansing tank 38. In other words, if the gap (clearance) is smallerthan the dimensions described above, the filtration media 14 will betrapped and crushed between the outer edge 54 of the blade 43 and theinner peripheral surface of the cleansing tank 38. This will precludethe obtainment of desired filtration function during filtration. If thegap is larger than the dimensions described above, the filtration media14 will drop through the gap, and not be discharged through the upperopenings 42 of the cleansing tank 38. That is, only the same filtrationmedia 14 will be cleansed, and the filtration media 14 to the exteriorof the cleansing tank 38 in the radial direction will not be cleansed.The manner of cleansing will be described later.

Next, the parts which are attached to the exterior of the filtrationtank 2 will be described with reference to FIG. 1. A downwardlyextending purified water discharge pipe 60 is mounted onto the center ofthe curved bottom wall 58 of the filtration tank 2. Purified water,which has passed through the filtration media 14, the filtration floor4, and the filters 12 are discharged via the purified water dischargepipe 60. A raw water filling opening 62 (contaminant expulsion means) ispositioned at the right side of the filtration tank in FIG. 1. Thefiltration tank 2 is filled with raw water, that is, unfiltered water16, through the raw water filling opening 62 during filtration. A waterlevel adjusting opening 64 is positioned below the raw water fillingopening 62. The water level adjusting opening 64 serves to optimize thewater level during cleansing of the filtration media 14, by expellingwater 16 from the filtration tank 2 therethrough. The amount of water 16necessary during cleansing is that which realizes fluidization of thefiltration media 14 at the upper openings 42 of the cleansing tank 38.However, if the amount of water 16 is excessive, the particle density ofthe filtration media 14 on the screw conveyor 32 is decreased. Thedecrease in particle density decreases opportunities for the particlesto scrub against one another, thereby deteriorating the cleansingefficiency. In the present embodiment, the ratio of filtration media 14to water 16 that yields the most efficient cleansing function is 2:1.

Reference numeral 68 in FIG. 1 denotes an inspection opening, which isutilized to inspect the state of the interior of the filtration tank 2.An air release valve 70 is positioned on the upper wall 20 of thefiltration tank 2, on the left side in FIG. 1. The air release valve 70enables filling of the filtration tank 2 with raw water, by expellingair within the filtration tank 2. During cleansing, the amount of rawwater is decreased. Therefore, at this time, air is caused to flow intothe filtration tank 2 from the exterior, to decrease the amount of rawwater without generating negative pressure. Reference numeral 72 denotesa filtration media filling opening.

Next, the filtration operation within the filtration tank 2 will bedescribed. First, the filtration tank 2 is filled with raw water throughthe war water filling opening 62, under pressure from a pump (notshown). As the water level 74 rises, air within the filtration tank 2 isexpelled through the air release valve 70. In the present embodiment,the water level 74 is set so that it rises above the raw water fillingopening 62 and reaches the upper portion of the filtration tank 2. Thatis, the water level 74 is set so that substantially the entirety of thefiltration tank 2 is filled with water 16 (raw water). The water level74 illustrated in FIG. 1 is at a position prior to the filtration tank 2being filled with water. The water 16 permeates the filtration media 14in the filtration tank 2, and also enters the cleansing tank 38 via theupper openings 42, to permeate the filtration media 14 within thecleansing tank 38. This enables filtration to be performed within thecleansing tank 38 as well. The water, which has permeated the filtrationmedia 14 and has been filtered, is discharged to the exterior via thepurified water discharge pipe 60, provided at the lower portion of thefiltration tank 2. The purified water is then utilized.

Next, the method of cleansing the filtration media 14, when thefiltration media 14 has been utilized over a long period of time andclogging is generated therein, will be described. Purified water isbackwashed through the purified water discharge pipe 60 prior to drivingthe motor 26 that rotates the screw conveyor 32, to cause the filtrationmedia 14 to float. Thereby, the load on the motor 26 during startup isreduced. When the motor 26 is driven, the screw conveyor 32 rotates. Thefiltration media 14 is conveyed upward to the interior of the cleansingtank 38, by the blade 43 of the rotating screw conveyor 32, particularlyby the portion of the blade 43 that protrudes below the cleansing tank38. The backwash of the purified water is continued during the initialstage of rotation of the screw conveyor 32. This is because mixing ofthe filtration media 14 at the radially outer and inner portions of thecleansing tank 38 is facilitated by rotating the screw conveyor 32 inthe backwash cleansing state, due to centrifugal force of the screwconveyor 32. At the same time, the entirety of the filtration media 14is thoroughly cleansed by this movement. The backwash of the purifiedwater is ceased thereafter. However, the rotation of the screw conveyor32 is continued to perform cleansing. The particles of the filtrationmedia 14 are conveyed upward by the rotation of the screw conveyor 32while rubbing against and scrubbing each other, and are discharged fromthe upper openings 42 into the filtration tank 2. Separation ofcontaminants from the filtration media 14 is enhanced by the impact ofthe filtration media 14 with the surface of the water 16. The filtrationmedia 14 which has dropped back into the filtration tank 2 is conveyedupwards into the cleansing tank 38 repeatedly, and scrubbed therein. Inthis manner, contaminants are separated from the filtration media 14 byrepetitive cleansing within the cleansing tank 38. As illustrated inFIG. 1, the lower end 44 of the screw conveyor 32 is positioned in thevicinity of the filtration floor 4. Therefore, the filtration media 14close to the filtration floor 4 is conveyed upward as well, therebythoroughly cleansing the entirety of the filtration media 14.

When cleansing is complete, purified water is backwashed through thepurified water discharge pipe 60 again. The backwash cleansing iscontinued after rotation of the screw conveyor 32 is ceased.Contaminants, which have been separated from the filtration media 14,are caused to float by the backwash, and are expelled to the exteriorthrough the raw water filling opening 62, along with water that containscontaminants. The water 16 is effectively backwashed through theinterior of the cleansing tank 38 as well, by passing through the gap 48of the blade 43. Therefore, contaminants within the cleansing tank 38are expelled as well. By continuing the backwash cleansing for apredetermined amount of time, all of the contaminants within thefiltration tank 2 are removed.

Next, replacement of the cleansing tank 38 and the screw conveyor 32when they become worn will be described. The cleansing tank 38 and thescrew conveyor 32 can be extracted to the exterior of the filtrationtank 2, by removing the bolts (not shown) that fix the base 28 and therim 24 to each other, and by removing the base 28 from the rim 24. Atthis time, the blade 43 of the screw conveyor 32 is buried in thefiltration media 14. Resistance against extraction is reduced bybackwash of purified water through the purified water discharge pipe 60,thereby causing the filtration media 14 to float. In this manner, thescrew conveyor 32 and the cleansing tank 38 may be easily extracted.Only the screw conveyor 32 may be removed, according to maintenancerequirements. When the screw conveyor 32 and the cleansing tank 38 arereinstalled, backwash of purified water through the purified waterdischarge pipe 60 is performed again. This causes the filtration media14 to float, thereby reducing the resistance against insertion by thefiltration media 14. In this manner, the screw conveyor 32 and thecleansing tank 38 may be easily reinstalled.

Next, a filtration apparatus 100 according to a second embodiment of thepresent invention will be described with reference to FIG. 4. Note thatthe parts of the filtration apparatus 100 which are in common with thoseof the first embodiment will be described by using the same referencenumerals. The filtration apparatus 100 differs from the filtrationapparatus 1 of the first embodiment in that a cleansing tank 138 extendsdownward longer than the cleansing tank 38, and a plurality of slots 176are provided therein. The slots 176 extend vertically, and are providedat the lower portion of the cleansing tank 138 at intervals along thecircumferential direction thereof. The vertical length of the blade 43,which is housed within the cleansing tank 138, can be extended, due tothe extended length of the cleansing tank 138. The cleansing function isimproved by this configuration, because the distance, over which thefiltration media 14 is scrubbed, is increased.

The slots 176 are formed to be of a size that allows the particles ofthe filtration media 14 to pass therethrough. The slots 176 facilitateentry of the filtration media 14 into the cleansing tank 138. The slots176 may be of any desired shape, such as elongated in the horizontaldirection. Entry of the filtration media 14 into the cleansing tank 13may be further facilitated, by setting a positional relationship inwhich the height of the upper edges 176 a of the slots 176 are above theupper surface 66 of the filtration media 14.

Next, a filtration apparatus 200 according to a third embodiment of thepresent invention will be described with reference to FIG. 5. FIG. 5 isa sectional view of the main parts of the filtration apparatus 200according to the third embodiment of the present invention. Thefiltration apparatus 200 differs from the filtration apparatuses of thefirst and second embodiments in that the screw conveyor is separableinto a plurality of parts. Thereby, assembly and disassembly of thefiltration apparatus is enabled within a space having a small verticalheight. Note that in the following description, the parts of thefiltration apparatus 200 which are in common with those of the previousembodiments will be described by using the same reference numerals.

As illustrated in FIG. 5, the filtration apparatus 200 comprises supportlegs 208, and a filtration tank 202. The filtration tank 202 is of alarger dimension in the vertical direction than those of the previoustwo embodiments. A filtration floor 204, which is similar to that of theprevious embodiments, is provided at the lower portion of the filtrationtank 202. A plurality of filters 12 are provided on the filtration floor204, as in the previous embodiments. A base 228, on which a motor 226and a brake mechanism 227 are mounted, is mounted on a rim 224 of theupper wall 220 of the filtration tank 202. The base 228 is of a similarconstruction as those of the previous two embodiments, and comprises aholding portion 236 (236 a and 236 b), which is separable in thevertical direction, for holding a screw conveyor 232. The details of thebase 228 and the holding portion 236 will be described later.

A cylindrical cleansing tank 238 and the screw conveyor 232 are placedin a mounting opening 222 formed by the rim 224. The cleansing tank 238is longer than those of the previous two embodiments, and the screwconveyor 232 protrudes downwardly through a lower opening 240 of thecleansing tank 238.

Next, the screw conveyor 232, the cleansing tank 238, and the base 228will be described in further detail, with combined reference to FIG. 6.FIG. 6 is a partial magnified view of the vicinity of the mountingopening 222. The mounting opening 222 is formed by the annular rim 224being welded to the upper end of the filtration tank 202. The rim 224comprises an upwardly facing step 278 at its inner periphery. Meanwhile,a flange 237 is welded to the outer periphery of the upper end of thecylindrical cleansing tank 238.

A downwardly facing annular step 280, which is complementary to the step278 of the rim 224, is formed at the outer periphery of the flange 237.The steps 278 and 280 are configured such that the step 280 is seated onthe step 278 when the cleansing tank 238 is inserted into the mountingopening 222 from above. The steps 278 and 280 are fixed to each other bya plurality of bolts 282, which are provided along the circumferentialdirection thereof. In this manner, the cleansing tank 238 is removablyattached to the filtration tank 202. Note that in the figures, only aportion of the bolts 282 is illustrated. As illustrated in FIG. 5, thelower opening 240 of the cleansing tank 238 is positioned above thefiltration floor 204. That is, a gap exists between the lower opening240 and the filtration floor 204. The lower end 235 of the screwconveyor 232 protrudes from the lower opening 240, to be positionedwithin this space. Note that the screw conveyor 232 will be described indetail later.

Next, the base 228 will be described with reference to FIG. 5 and FIG.6. The base 228 comprises an upper base 228 a and a lower base 228 b(refer to FIG. 6). The upper base 228 a comprises a cylindrical member284 a, an annular member 286 a, and an annular member 286 b. The annularmembers 286 a and 286 b are welded to the upper and lower ends of thecylindrical member 284 a, respectively. The upper annular member 286 a,the lower annular member 286 b, and the cylindrical member 284 a arereinforced by a plurality of reinforcement ribs 288 a, which areprovided along the circumferential direction and welded perpendicularlythereto. The lower base 228 b comprises a cylindrical member 284 b, anannular member 286 c (partition wall), and an annular member 286 d(partition wall) The cylindrical member 284 b has a shorter dimension inthe vertical direction than the cylindrical member 284 a. The annularmembers 286 c and 286 d are welded to the upper and lower ends of thecylindrical member 284 b, respectively. The annular member 286 c, theannular member 286 d, and the cylindrical member 284 b are reinforced bya plurality of reinforcement ribs 288 b, which are provided along thecircumferential direction and welded perpendicularly thereto.

The upper base 228 a and the lower base 228 b are linked by a pluralityof sets of bolts 290 and nuts 291, which are provided along thecircumferential direction of the annular members 286 b and 286 c,thereby constructing the integrated base 228. The base 228 is mounted tothe filtration tank 202 by the annular member 286 d being fixed to therim 224 with the plurality of bolts 292, which are provided along thecircumferential direction of the rim 224. That is, the annular member286 d is mounted to the filtration tank 202 by the bolts 292, at aflange portion that protrudes outward from the outer periphery of thecylindrical member 284 b. Note that a channel 287 is provided within theannular member 286 d so as to communicate the interior and the exteriorof the cylindrical member 284 b. The channel 287 serves as a drain forexpelling water that enters the cylindrical member 286 d.

Referring again to FIG. 5, the motor 226 and the brake mechanism 227,which is integral with the motor 226, are mounted on the base 228, whichis mounted on the filtration tank 202 in this manner, with bolts (notshown). A rotating shaft 293 of the brake mechanism 227 and a shaft 234of the screw conveyor 232 are linked via a coupling 252.

Next, the screw conveyor 232 and a support structure therefor will bedescribed. As illustrated in FIG. 5, the screw conveyor 232 comprises anupper shaft 234 a and a lower shaft 234 b. The upper shaft 234 a is heldby the holding portion 236. The lower shaft 234 b is detachably linkedto the upper shaft 234 a. The screw conveyor 232 differs from those ofthe previous two embodiments in that the upper shaft 234 a and the lowershaft 234 b are separable at a separating portion 294. The separatingportion 294 enables separation of the upper and lower shafts 234 a and234 b, by linking the two at flanges 294 a and 294 b with bolts 295. Theflange 294 a is formed at the lower end of the upper shaft 234 a, andthe flange 294 b is formed at the upper and of the lower shaft 234 b.The reason that the screw conveyor 232 is provided to be separable willbe described later. A spiral blade 243 is formed on the screw conveyor232 to the lower end 244 of the shaft 234, in a similar manner to thoseof the previous two embodiments. The separating portion 294 is providedat a portion of the shaft 234 where the blade 243 is not formed, in thevicinity of the upper end of the blade 243. This is in order to secureas long a dimension as possible for the blade 243, while effectivelyreducing the dimensions of the shaft 234 after separation. As a result,the separating portion 294 is positioned in the vicinity of the upperends of upper openings 242 of the cleansing tank 238.

Next, the holding portion 236 will be described with reference to FIG. 5and FIG. 6. The upper holding portion 236 a comprises a cylindrical mainbody 298 and tapered roller bearings 296 at the upper and lower endsthereof. The tapered roller bearings 296 rotatably hold the upper shaft234 a of the shaft 234 in a vertical orientation. The tapered rollerbearings 296 are provided within recesses 298 a, which are formed in theupper and lower ends of the main body 298. Annular plates 300 are fixedto the upper and lower ends of the main body 298 with screws 302. Theannular plates 300 serve to prevent extraction of the tapered rollerbearings 296. A plurality of vertically extending ribs 304 are weldedalong the outer periphery of the main body 298. Each of the ribs 304 hasa horizontally fixing piece 306 at the lower end thereof. The fixingpieces 306 are fixed to the annular member 286 c with bolts 308. In thismanner, the upper holding portion 236 a is fixed to the lower base 228b.

Next, the lower holding portion 236 b will be described. A circularaperture 333 for housing the lower holding portion 236 b is formed inthe annular member 286 d. The lower holding portion 236 b comprises acylindrical main body 312 that extends in the axial direction of theupper holding portion 236 a. The lower holding portion 236 b is placedwithin the aperture 333 and fixed thereto by welding. At the same time,ribs 314 are welded to the main body 312 and the annular member 236 d,to strengthen the link between the main body 312 and the annular member286 d. Packing material 316 is provided between the main body 312 andthe shaft 234, in the upper portion of the main body 312. The packingmaterial 316 is held by a cylindrical stop 318 of an extractionpreventing member 320. The extraction preventing member 320 is fixed tothe annular member 286 d with screws 322, which are held in a flange 319that protrudes from the stop 318. A bearing 326 is provided in a space324 at the lower portion of the main body 312. An oil seal 328 isprovided below the bearing 326. A discoid plate 332 having an opening330 formed therein is provided below the oil seal 328. The discoid plate332 serves to prevent extraction of the oil seal 328. The shaft 234penetrates the opening 330, and the discoid plate 332 is fixed to themain body 312 with screws 334.

There are cases in which the filtration apparatus 200, which isconstructed in the manner described above, is installed and utilizedindoors. After a predetermined period of use in this utilization state,it becomes necessary to perform maintenance and replacement of the screwconveyor 232 and the like, which become worn. The steps involved in thedisassembly process of the filtration apparatus 200 for maintenanceoperations will be described with reference to FIG. 7 through FIG. 10.FIG. 7 is a sectional view of the main parts of the filtration apparatus200, illustrating the process of removing the motor 226 therefrom. FIG.8 is a sectional view of the main parts of the filtration apparatus 200,illustrating the process of removing the base 228 therefrom. FIG. 9 is asectional view of the main parts of the filtration apparatus 200,illustrating the process of removing the lower shaft 234 b therefrom.FIG. 10 is a sectional view of the main parts of the filtrationapparatus 200, illustrating the process of removing the cleansing tank238 therefrom.

First, a description will be given with reference to FIG. 7. The motor226 is removed from the base 228 as indicated by arrow A, by removingthe bolts (not shown) that fix the motor 226 to the vase 228. At thistime, the coupling 252 is prepared for separation, by removing a bolt(not shown) in advance.

Next, as illustrated in FIG. 8, the bolts 292 (refer to FIG. 6) that fixthe base to the rim 224 are removed. Then, the base is suspended by ahook 346 engaging a rope or a wire 344, which is fed through eye bolts342. The hook 346 is provided as part of a conveyance apparatus 340(geared trolley), which is mounted on a rail 338 of the ceiling 336 of abuilding. At this time, the screw conveyor 232, which is held by theholding portion 236, is also drawn upward. However, the screw conveyor232 cannot be completely extracted, due to the relationship between thelength thereof and the height of the ceiling. Therefore, a temporarybase 348 is mounted on the rim 224 after the screw conveyor 232 is drawnout to a predetermined height. The screw conveyor 232 is temporarilyplaced on the temporary base 348. The flange 294 b of the separatingportion 294 of the shaft 234 is placed on the temporary base 348.

The temporary base 348 is configured to be separable in the directionperpendicular to the axial direction of the shaft 234. When assembled,an opening 350 for receiving the shaft 234 is formed in the upperportion of the temporary base 348. The flange 294 b is placed on theperipheral edge of the opening 350. It is preferable that the temporarybase 348 is a cylindrical member. The cylindrical temporary base 348 isconstituted of two parts, and is provided on the rim 224 from both sidesof the shaft 234. The temporary base 348 may be constructed from aplurality of members having legs that abut the rim 224, as analternative to the cylindrical construction.

After the base 228 is placed on the temporary base 348, the bolts 295that link the separating portion 294, thereby separating the upper shaft234 a from the lower shaft 234 b. In this manner, the base 228 and theupper shaft 234 a are enabled to be moved horizontally in the directionindicated by arrow B, without lifting them any higher. At this time, thelower shaft 234 b is left in a state in which it is supported by thetemporary base 348.

Then, as illustrated in FIG. 9, the lower shaft 234 b is lifted andremoved from the cleansing tank 238 by the conveyance apparatus 340 orthe like, at the same time that the temporary base 348 is removed fromthe rim 224.

Thereafter, as illustrated in FIG. 10, the bolts 282 that fix thecleansing tank 238 to the rim 224 are removed, and the cleansing tank238 is extracted upward from the mounting opening 222.

In this manner, it is possible to sequentially remove each part from themounting opening 222 of the filtration tank 202 when performingmaintenance operations. This enables extremely efficient operations.Particularly, because the screw conveyor 232 is of a separablestructure, the operations can be performed even indoors, with arelatively low ceiling. Note that the manner in which filtration andfiltration media cleansing is performed is the same as those of theprevious two embodiments.

As described above, in the third embodiment, the shaft 234 is of aseparable structure, which yields good maintenance properties.Therefore, an advantageous effect is exhibited in that a cleansing tank202 having good filtration efficiencies, by virtue of being long in thevertical direction, may be utilized even indoors, with a relatively lowceiling.

The preferred embodiments of the present invention have been describedin detail above. However, the present invention is not limited to theconfigurations described above. For example, the lower ends 44 and 244of the screw conveyors 32 and 232 are free ends. However, aconfiguration may be adopted wherein the lower ends 44 and 244 aresupported. Specifically, the lower ends 44 and 244 maybe conical inshape, and a member having a recess for receiving the tip of the conemay be provided on the filtration floors 4 and 204. By thisconfiguration, horizontal displacement of the screw conveyors 32 and 232may be further suppressed. In addition, this configuration poses noobstacles to the replacement of the screw conveyors 32 and 232, and thecleansing tanks 38, 138, and 238.

In addition, the screw conveyors 32 and 232 are capable of conveying thefiltration media 14 upward without necessarily protruding downwardbeyond the cleansing tanks 38, 138, and 238. In this case, thefiltration media 14 is enabled to enter the cleansing tanks 38, 138, and238 with relatively lower resistance by providing the lower ends 44 and244 of the screw conveyors 32 and 232 above the filtration floors 4 and204 at a distance.

It is preferable that the positions of the upper openings 42 are not toolow. This is to enable scrubbing of the filtration media 14 over alonger distance within the cleansing tanks 38, 138, and 238. Inaddition, the manner of attachment between the cleansing tanks 38, 138,and 238 and the mounting openings are not limited to those of theembodiments described above. Various constructions may be consideredthat enable easy assembly and disassembly.

Note that in the above embodiments, cases in which water is filteredwere described. However, the filtration apparatus of the presentinvention may be utilized to filter liquids other than water, such asoil.

Further, the cleansing portion includes the cleansing tanks 38, 138, and238, the screw conveyors 32 and 232, and the drive mechanisms for thescrew conveyors 32 and 232. However, the motors 26 and 226 are notnecessarily included. In the case that the motors 26 and 226 are notincluded, they may be directly provided on the filtration tanks 2 and202. In this case, the rotation of the motors is transferred to thescrew conveyors via link portions. When the drive portions and themotors 26 and 226 are disassembled, the disassembly may be performed atthe link portions.

Next, a modification of the present invention will be described withreference to FIG. 11. FIG. 11 is a sectional view of the main parts of afiltration apparatus 400 according to a modification of the presentinvention, in which a cleansing portion and a filtration tank are shownseparately. The filtration apparatus 400 comprises a filtration tank402, which is similar to the filtration tank 2. The filtration tank 402comprises: a raw water filling opening 462; two filtration floors 404and 407, which are separated in the vertical direction; strainers 412,which are provided on the lower filtration floor 404; a purified waterdischarge pipe 460 for discharging filtered water; and an air releasevalve 470. Two filtration floors are provided in the filtrationapparatus 400. Filtration media 414 is housed above the upper filtrationfloor 407, and filtration media 454 is housed between the lowerfiltration floor 404 and the upper filtration floor 407.

A circular mounting opening 422 is formed at the center of the upperwall 420 of the filtration tank 402. A cleansing portion 403 (cleansingmeans), which is shown to the right of the filtration tank 402 separatedtherefrom, is mounted on the mounting opening 422. The peripheral edgeof the mounting opening 422 is formed into a mounting rim 424. A discoidlid 405 is fixed on the rim 424 by a plurality of bolts 492, which areprovided at predetermined intervals along the rim 424. In this manner,the mounting opening 422 is closed by the lid 405 during filtration.Accordingly, the filtration apparatus 400 does not comprise thecleansing portion 403 during filtration.

When the filtration apparatus 400 is utilized to filter water 416(liquid), the filtration tank 402 is filled with the water 416 throughthe raw water filling opening 462. The raw water 416 is filtered bypassing through the filtration media 414 and 454, then filtered water isdischarged through the purified water discharge pipe 460.

Next, the cleansing portion 403 will be described. The cleansing portion403 is of a similar construction to the cleansing portions of thefiltration apparatuses 1, 100, and 200 illustrated in FIG. 1, FIG. 4,and FIG. 7. The cleansing portion 403 comprises: a motor 426 (driveportion); a brake mechanism 427 (drive portion) for decelerating therotation of the motor 426; and a base 428 for supporting the motor 426and the brake mechanism 427. A cylindrical cleansing tank 438 is mountedon the base 428. A screw conveyor 432, which is linked to the brakemechanism 427 via a coupling 452 and which is rotated by the motor 426,is provided within the cleansing tank 438. The base 428 of the cleansingportion 403 further comprises a flange 409 for mounting onto the rim424. Apertures (not shown) are formed in the flange 409, at the sameintervals as those of the bolts in the lid 405.

Next, a case in which the filtration media 414 and 454, which havecontaminants trapped therein after a predetermined period of use, arecleansed, will be described. First, the lid 405 is removed, and themounting opening 422 is exposed. Then, the cleansing tank 438 of thecleansing portion 403 is inserted through the mounting opening 422. Theflange 409 of the cleansing portion 403 is placed on the rim 424 andbolted thereto, to fix the cleansing portion 403 to the filtration tank402. Thereafter, the cleansing portion 403 is operated as in theprevious embodiments, and the filtration media 414 is cleansed. Notethat in FIG. 11, reference numeral 471 denotes an ultrasonic wavegenerating apparatus that separates contaminants from the filtrationmedia 454 with ultrasonic vibrations.

The cleansing operation performed by the cleansing portion 403 issimilar to those of the previous embodiments, and a rough descriptionthereof is as follows. First, backwash of purified water is performedthrough the purified water discharge pipe 460 to cause the filtrationmedia 414 to float, prior to driving the motor 426 that rotates thescrew conveyor 432. Thereby, the load on the motor 426 during startup isreduced. When the motor 426 is driven, the screw conveyor 432 rotates.The filtration media 414 is conveyed upward to the interior of thecleansing tank 438, by a blade 443 of the rotating screw conveyor 432,particularly by the portion of the blade 443 that protrudes below thecleansing tank 438. The backwash of the purified water is continuedduring the initial stage of rotation of the screw conveyor 432. This isbecause mixing of the filtration media 414 at the radially outer andinner portions of the cleansing tank 438 is facilitated by rotating thescrew conveyor 432 in the backwash cleansing state, due to centrifugalforce of the screw conveyor 432. At the same time, the entirety of thefiltration media 414 is thoroughly cleansed by this movement. Thebackwash of the purified water is ceased thereafter. However, therotation of the screw conveyor 432 is continued for a short timethereafter, to perform cleansing.

The particles of the filtration media 414 are conveyed upward by therotation of the screw conveyor 432 while rubbing against and scrubbingeach other, and are discharged from upper openings 442 of the cleansingtank 438 into the filtration tank 402. Separation of contaminants fromthe filtration media 414 is enhanced by the impact of the filtrationmedia 414 with the surface of the water 416. The filtration media 414which has dropped back into the filtration tank 402 is conveyed upwardsinto the cleansing tank 438 repeatedly, and scrubbed therein. In thismanner, contaminants are separated from the filtration media 414 byrepetitive cleansing within the cleansing tank 438. At this time,contaminants within the filtration media 454 may be effectively removedby vibrations generated by the ultrasonic wave generating apparatus 471.As illustrated in FIG. 11, the lower end 444 of the screw conveyor 432is positioned in the vicinity of the filtration floor 407. Therefore,the filtration media 414 close to the filtration floor 407 is conveyedupward as well, thereby thoroughly cleansing the entirety of thefiltration media 414, in a similar manner as in the previousembodiments.

When cleansing is complete, purified water is backwashed through thepurified water discharge pipe 460 again. The backwash cleansing iscontinued after rotation of the screw conveyor 432 is ceased.Contaminants, which have been separated from the filtration media 414,are caused to float by the backwash, and are expelled to the exteriorthrough the raw water filling opening 462, along with water thatcontains contaminants. By continuing the backwash cleansing for apredetermined amount of time, all of the contaminants within thefiltration tank 402 are removed.

When the cleansing and rinsing of the filtration media 414 and 454 arecomplete, the cleansing portion 403 is removed, the lid 405 is mountedon the rim 424, and the mounting opening 422 is closed. In this manner,the filtration apparatus 400, which does not comprise the cleansingportion 403, is suited for a manner of use in which cleansing isperformed only during annual maintenance, for example. As the cleansingportion 403 is unnecessary at the time of initial installment, thefiltration apparatus 400 may be provided at low cost.

1. A filtration apparatus comprising a filtration tank for filtering aliquid which is introduced into filtration tank, and discharging thefiltered liquid to an exterior of the filtration tank comprises:filtration media contained in the filtration tank; a filtration mediacleansing mechanism that comprises a hollow cleansing tank for cleansingthe filtration media, and a contaminant expulsion means for expellingcontaminants separated from the filtration media to the exterior to thefiltration tank; wherein: the cleansing tank is a cylindrical body thathangs within the filtration tank from an upper portion thereof, thecleansing tank is provided with a lower opening at a position lower thatan upper surface of the filtration media housed in the filtration tank,and a plurality of upper openings at a position higher than the uppersurface of the filtration media, and the cleansing tank is provided witha screw conveyor for conveying the filtration media and the liquid,which enter the cleansing tank from the filtration tank via the loweropening, upward from the lower opening to the upper openings whilescrubbing the filtration media within the cleansing tank; a mountingopening, to which the upper portion of the cleansing tank is removablyattachable, provided at the upper portion of the filtration tank; and acleansing portion, comprising the cleansing tank, the screw conveyor,and a drive mechanism for the screw conveyor, removably attachable tothe filtration tank via the mounting opening, from the exterior of thefiltration tank.
 2. A filtration apparatus as defined in claim 1,wherein: the lower end of the screw conveyor protrudes downward from thelower opening of the cleansing tank.
 3. A filtration apparatus asdefined in claim 2, wherein: the cleansing portion is constructed by aplurality of parts, which are detachably linked so as to separate in theaxial direction of the screw conveyor.
 4. A filtration apparatus asdefined in claim 3, wherein: slots that enable the filtration media topass therethrough are formed at the lower portion of the cleansing tankso that at least a portion of the slots are below the upper surface ofthe filtration media.
 5. A filtration apparatus as defined in claim 4,wherein: a plurality of gaps that extend along the outer periphery ofthe axis of the screw conveyor are formed in the interior sides of theblades of the screw conveyor.
 6. A filtration apparatus as defined inclaim 3, wherein: a plurality of gaps that extend along the outerperiphery of the axis of the screw conveyor are formed in the interiorsides of the blades of the screw conveyor.
 7. A filtration apparatus asdefined in claim 2, wherein: slots that enable the filtration media topass therethrough are formed at the lower portion of the cleansing tankso that at least a portion of the slots are below the upper surface ofthe filtration media.
 8. A filtration apparatus as defined in claim 7,wherein: a plurality of gaps that extend along the outer periphery ofthe axis of the screw conveyor are formed in the interior sides of theblades of the screw conveyor.
 9. A filtration apparatus as defined inclaim 2, wherein: a plurality of gaps that extend along the outerperiphery of the axis of the screw conveyor are formed in the interiorsides of the blades of the screw conveyor.
 10. A filtration apparatus asdefined in claim 1, wherein: the cleansing portion is constructed by aplurality of parts, which are detachably linked so as to separate in theaxial direction of the screw conveyor.
 11. A filtration apparatus asdefined in claim 10, wherein: slots that enable the filtration media topass therethrough are formed at the lower portion of the cleansing tankso that at least a portion of the slots are below the upper surface ofthe filtration media.
 12. A filtration apparatus as defined in claim 11,wherein: a plurality of gaps that extend along the outer periphery ofthe axis of the screw conveyor are formed in the interior sides of theblades of the screw conveyor.
 13. A filtration apparatus as defined inclaim 10, wherein: a plurality of gaps that extend along the outerperiphery of the axis of the screw conveyor are formed in the interiorsides of the blades of the screw conveyor.
 14. A filtration apparatus asdefined in claim 1, wherein: slots that enable the filtration media topass therethrough are formed at the lower portion of the cleansing tankso that at least a portion of the slots are below the upper surface ofthe filtration media.
 15. A filtration apparatus as defined in claim 14,wherein: a plurality of gaps that extend along the outer periphery ofthe axis of the screw conveyor are formed in the interior sides of theblades of the screw conveyor.
 16. A filtration apparatus as defined inclaim 1, wherein: a plurality of gaps that extend along the outerperiphery of the axis of the screw conveyor are formed in the interiorsides of the blades of the screw conveyor.
 17. A filtration apparatuscomprising a filtration tank containing filtration media for filtering aliquid which is introduced into the filtration tank, and discharging thefiltered liquid to an exterior of the filtration tank, wherein thefiltration tank comprises: a mounting opening that the filtration mediais visible through provided in the filtration tank above the filtrationmedia; a removably attachable lid provided to cover the mountingopening; and a cleansing portion having a hollow cleansing tank, a screwconveyor for conveying the filtration media and the liquid upward whilescrubbing the filtration media within the cleansing tank, and a drivingmechanism for driving the screw conveyor, wherein the cleansing portionis structured so that the lid is removed only when the filtration mediais cleansed, and the cleansing portion is inserted into the mountingopening from outside for cleansing the filtration media.